COVID-19 can cause severe neurological symptoms, but the underlying pathophysiological mechanisms are unclear. Here, we interrogated the brain stem and olfactory bulb in COVID-19 patients postmortem using imaging mass cytometry to understand the local immune response at a spatially resolved, high-dimensional single-cell level and compared their immune map to non-COVID respiratory failure, multiple sclerosis and control patients. We observed substantial immune activation in the central nervous system with pronounced neuropathology (astrocytosis, axonal damage, blood-brain-barrier leakage) and detected viral antigen in ACE2 receptor-positive cells enriched in the vascular compartment. Microglial nodules and the perivascular compartment represented COVID-19-specific microanatomic immune niches with context-specific cellular interactions enriched for activated CD8 + T cells. Altered brain T cell–microglial interactions were linked to clinical measures of systemic inflammation and disturbed hemostasis. This study identifies profound neuroinflammation with activation of innate and adaptive immune cells as correlates of COVID-19 neuropathology, with implications for potential therapeutic strategies.

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Zinc deficiency has a fundamental influence on the immune defense, with multiple effects on different immune cells, resulting in a major impairment of human health. Monocytes and macrophages are among the immune cells that are most fundamentally affected by zinc, but the impact of zinc on these cells is still far from being completely understood. Therefore, this study investigates the influence of zinc deficiency on monocytes of healthy human donors. Peripheral blood mononuclear cells, which include monocytes, were cultured under zinc deficient conditions for 3 days. This was achieved by two different methods:by application of the membrane permeable chelator N,N,N 0 ,N 0 -tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) or by removal of zinc from the culture medium using a CHELEX 100 resin. Subsequently, monocyte functions were analyzed in response to Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Zinc depletion had differential effects. On the one hand, elimination of bacterial pathogens by phagocytosis and oxidative burst was elevated. On the other hand, the production of the inflammatory cytokines tumor necrosis factor (TNF)-a and interleukin (IL)-6 was reduced. This suggests that monocytes shift from intercellular communication to basic innate defensive functions in response to zinc deficiency.These results were obtained regardless of the method by which zinc deficiency was achieved. However, CHELEX-treated medium strongly augmented cytokine production, independently from its capability for zinc removal. This side-effect severely limits the use of CHELEX for investigating the effects of zinc deficiency on innate immunity.

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Conserved HLA class I epitopes were defined by screening a norovirus peptide library. HLA-peptide tetramers tracked norovirus-specific CD8 þ T cells with diverse differentiation states across lymphoid and intestinal tissues. These reagents can enhance future vaccine studies and cell-based treatment approaches.BACKGROUND & AIMS: Noroviruses (NoVs) are the leading cause of acute gastroenteritis worldwide and are associated with significant morbidity and mortality. Moreover, an asymptomatic carrier state can persist following acute infection, promoting NoV spread and evolution. Thus, defining immune correlates of NoV protection and persistence is needed to guide the development of future vaccines and limit viral spread.Whereas antibody responses following NoV infection or vaccination have been studied extensively, cellular immunity has received less attention. Data from the mouse NoV model suggest that T cells are critical for preventing persistence and achieving viral clearance, but little is known about NoV-specific T-cell immunity in humans, particularly at mucosal sites. METHODS:We screened peripheral blood mononuclear cells from 3 volunteers with an overlapping NoV peptide library. We then used HLA-peptide tetramers to track virus-specific CD8 þ T cells in peripheral, lymphoid, and intestinal tissues. Tetramer þ cells were further characterized using markers for cellular trafficking, exhaustion, cytotoxicity, and proliferation. RESULTS:We defined 7 HLA-restricted immunodominant class I epitopes that were highly conserved across pandemic strains from genogroup II.4. NoV-specific CD8 þ T cells with central, effector, or tissue-resident memory phenotypes were present at all sites and were especially abundant in the intestinal lamina propria. The properties and differentiation states of tetramer þ cells varied across donors and epitopes. CONCLUSIONS:Our findings are an important step toward defining the breadth, distribution, and properties of human NoV T-cell immunity. Moreover, the molecular tools we have developed can be used to evaluate future vaccines and engineer novel cellular therapeutics.

The immune-pathology in Crohn’s disease is linked to dysregulated CD4+ T cell responses biased towards pathogenic TH17 cells. However, the role of CD8+ T cells able to produce IL-17 (Tc17 cells) remains unclear. Here we characterize the peripheral blood and intestinal tissue of Crohn’s disease patients (n = 61) with flow and mass cytometry and reveal a strong increase of Tc17 cells in active disease, mainly due to induction of conventional T cells. Mass cytometry shows that Tc17 cells express a distinct immune signature (CD6high, CD39, CD69, PD-1, CD27low) which was validated in an independent patient cohort. This signature stratifies patients into groups with distinct flare-free survival associated with differential CD6 expression. Targeting of CD6 in vitro reduces IL-17, IFN-γ and TNF production. These results identify a distinct Tc17 cell population in Crohn’s disease with proinflammatory features linked to disease activity. The Tc17 signature informs clinical outcomes and may guide personalized treatment decisions.

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Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are rare, autoimmune mediated cholestatic liver diseases. Other auto-immune diseases are often associated with PBC and PSC, and inflammatory bowel disease is present in the majority of PSC patients. In the course of disease, chronic inflammation in the liver leads to fibrotic restructuring and ultimately cirrhosis. The diagnosis of PBC is confirmed serologically and PSC is diagnosed via cholangiography, whereas MRCP is preferred over ERCP. For PBC, the first line therapy is ursodeoxycholic acid (UDCA). Prognosis is strongly dependent on the response to UDCA. The only approved second line therapy is obeticholic acid (OCA). Alternatively, Budesonide or Fibrates are often used off-label. In the management of PSC, prevention and adequate treatment of bacterial cholangitis play a major role. For both PBC and PSC novel treatments are currently being tested in clinical trials. Disease management should address compromising symptoms like pruritus and sicca as well as complications due to maldigestion and concomitant autoimmune diseases. The only curative treatment available is liver transplantation and should be considered at a MELD score of 15.